This application claims priority of the German utility model application 202 00 079.6 which is incorporated by reference herein.
The invention concerns a stand having an automatic balancing device. In the field of surgical microscopes in particular, increasing use is being made of stands that balance out the weight of the microscope by means of an automatic balancing device. In this context, counterweights are displaced as a function of forces or moments that result from an imbalance, so that the load (microscope and its accessories) and the counterweights end up in a balanced-out state. This state is achieved when a user can move the microscope on the stand in three dimensions as if it were weightless. Brakes that lock the stand in a selected position in three dimensions are also, as a rule, provided in addition to the automatic balancing device.
Conventional stands are braked during the automatic balancing process by means of at least one of the brakes. The imbalance is then measured (by measuring e.g. flexural, rotational, or inflection moments or forces). A computer then ascertains, for example with reference to a table, whether the stand is in balance or imbalance. If the stand is in imbalance, an adjustment command is generated for an adjustment motor, which adjusts at least one of the counterweights in such a way that the imbalance becomes smaller. If necessary, this operation is repeated until the imbalance is reduced to a minimum.
Since the measurement of the imbalance is performed with the load and the counterweight in the braked, stationary state, this automatic balancing method is a static measurement and control method. The inventor therefore refers to the known balancing method as the xe2x80x9cstatic balancing method.xe2x80x9d
Balancing methods are used, for example, in the OHS of Leica Microsystems (brochure no. 10M15010EN) and in the assemblage of DE 43 20 443 C2.
The inventor has recognized that the known systems are disadvantageous in the following ways:
a) The procedure of measurement, calculation, activation, and adjustment takes time. Users, however, would like to have immediate and complete balancing without having to allow time to elapse.
b) During stepwise resolution of the measurement, activation, and adjustment operation, in particular during repetition in multiple steps, in extreme cases a vibration that is unpleasantly perceptible, and can even have a negative influence on the measurement, can be generated in the stand.
c) To eliminate the problem set forth in b), the counterweight must be moved slowly; this aggravates the problem described in a).
It is thus the object of the invention to create an apparatus which eliminates the disadvantages cited, by the fact that the automatic balancing operation is to be accelerated and the time necessary therefor is reduced, and by the fact that the stepwise resolution of the balancing operation is to be converted as much as possible into a continuous operation.
This object is achieved by modifying the conventional balancing device to create a xe2x80x9cdynamic balancing operationxe2x80x9d in which:
i) measurement of a static imbalance state is dispensed with;
ii) adjustment of the counterweight is performed continuously during balancing; and
iii) during adjustment of the counterweight, the imbalance is measured dynamically as it changes.
iv) Comparison with tables, calculation of adjustment commands, etc. can be dispensed with. (Such operations can, however, also be provided for in dynamic balancing, although they do not constitute the basis of the system according to the present invention; they can in some circumstances serve merely to refine or improve the system. What is critical is that in the context of the invention, measurement occurs during adjustment and not with the stand in the static state.)
A new stand according to a described embodiment the present invention generally comprises an automatic balancing device in which a counterweight (AG) is displaceable on an effective lever arm (h) by an electric motor (5) and in which the electric motor (5) can be activated by means of a sensor (8) and microprocessor (12) via control lines (13), the microprocessor (12) executing a software program. The new stand is characterized in that the software program comprises program steps in which, as adjustment of the counterweight (AG) to modify the effective lever arm (h) is proceeding, the measured imbalance at the sensor (8) is ascertained, and the signal value thus dynamically measured is used for activation of the electric motor (5), the continuing adjustment motion of the electric motor (5) being influenced as necessary by the activation.
Further embodiments and developments of the invention are described herein.
The following improvements are achieved as a result of the new configuration of the stand with the new balancing philosophy, as described above:
Complete balancing of a stand is accomplished more quickly;
The system has less tendency to oscillate, and measurement results are more exact;
The new system requires less computer performance and is thus also less susceptible to malfunction;
As a result of the dynamic measurement and adjustment operation, the speed can be optimally adapted to the vibration behavior of the overall system. No abrupt stops occur during adjustment motion.
Although the text above and below refers to stands for surgical microscopes, the invention is nevertheless not limited thereto, but on the contrary is also available to other users of optical devices with stands and automatic balancing operations (e.g. telescopes, projectors, video and photographic cameras, etc.). The claims are thus to be construed correspondingly broadly.
The Parts List and the Figures, together with the subject matters described and protected in the Claims and the Utility Model applications referred to for the Applicant""s MS-2, are an integral constituent of the disclosure of this Application.